1. Field of the Invention
The present invention relates to an industrially advantageous process for preparing an imidazole derivative which is useful as an intermediate for the preparation of biotin (vitamin H).
2. Description of Prior Art
JP-A-61-151194 discloses a process for the preparation of an imidazole derivative of the formula (1): ##STR3## wherein R.sup.1 and R.sup.2 are the same or different and each represents a hydrogen atom or an alkyl, aryl, acyl or aralkyl group, X and Y are the same or different and each an oxygen or sulfur atom, and Z is a substituted alkyl group, which comprises catalytically reducing a corresponding precursor in an alcoholic solvent using a palladium catalyst. The palladium catalyst has the superior catalytic activity to other catalysts, while removal of the spent catalyst from the reaction mixture is difficult. Therefore, the above disclosed process removes the spent catalyst from the reaction mixture by replacing the alcoholic solvent with other solvent such as toluene.
However, the above disclosed process is not satisfactory as the industrial process since it requires the troublesome and time consuming procedures for the evaporation of the alcoholic solvent and the addition of the other solvent, and also the number of process steps such as the steps for recovering and recycling the solvents increases because of the use of a plurality of the solvents.